The reason I thought an out and back would be better was due to cost. For the cost of a plane ticket for me and my bike to fly back, I could ride back.
Given that you can get a flight on Southwest from Columbus,OH to the Portland, OR for $205 plus $75 for the bike, you really can't expect to save much money. Also you are planning a long way in the future, so putting aside $280 for air travel should be pretty easy.
If you were doing it only for the challenge of doing the miles in that time, I could maybe see it, but to save money? That sounds like a bad idea.
I'll add that it was kind of a grind doing the TA one way in 73 days. It was fun but it wasn't like we felt like we were taking it especially easy. I mat a few people on the TA who had planned to do 100+ mile day average and all of them eventually settled into something more like 80 MPD.
My advice, put aside a few bucks enjoy the ride and fly one way.